1. Field of the Invention
The present invention relates to radio frequency identification (RFID) systems for identification, marking and tracking of selected items, and more specifically to one embodiment of such a system for locating pipelines and components thereof of the type used in water, sewage and other types of fluid conveyance systems.
2. Description of the Prior Art
There exists a need in a number of different industries for improvements in the way that items are identified, marked and tracked. This is especially true where a large number of items must be separated, identified, counted and sorted. One example is the manufacture of sealing gaskets for use in water, sewage and fluid conveyance systems generally. Present day means for solving this problem typically use manual workers who sequentially sort amongst the many items, picking single items manually and identifying the items visually. This solution is unsatisfactory because it is both slow and expensive, due to the high reliance on manual labor, and because mistakes occur in identifying and sorting the items. There is also a need for inventory control, for example, at the wholesaler's warehouse.
Various solutions have been proposed to automate the above process which involve the use of either bar codes or various other types of optical readers. For example, identification schemes which relay upon reading bar codes or other optical indicia are not well suited for use in the sorting of flat goods rather than contoured items. However, in the case of gasket manufacture, the items in question range in size from very small to large and are typically processed in a variety of orientations which are problematical for line of sight reading devices. There are other barriers and obstacles to the accurate machine identification and automated counting and sorting of sealing gaskets of the type under consideration.
For example, sealing gaskets are typically either extruded or compression molded, both being relatively high temperature and pressure operations. Whether the identifying “tag” is molded into the rubber of the gasket or merely affixed in some way to the gasket exterior, it must be robust enough in construction to withstand the influences present in the normal manufacturing environment The tag must also be provided at an acceptable cost to allow it to be utilized in mass production operations. These type demands have frustrated efforts to adapt bar codes and other optical indicia to sealing gasket technology. The lack of a viable coding and sorting solution for this segment of the fluid conveyance and sealing technologies has resulted in high labor costs, lack of stock control, and reduced profits.
A need thus exists for a marking and tracking technology that has the ease of use and the low cost associated with bar codes, and yet is more robust and tolerant of the conditions found in large scale industrial manufacturing plants for sealing gaskets and other similar environments.
There is also a need for improvements in the way pipelines and components of pipelines are located, including underground municipal piping having sealing gaskets of the aforementioned type. Municipal piping constitutes the form of transportation that is used to provide liquids, such as water, and gases, such as natural gas, to residential or commercial properties. Piping of this general type also removes waste from the household in the form of sewage. Such pipelines also include plastic fittings as components thereof.
In the case of municipal piping, it is a common practice to bury the water, gas and sewer pipes underground, as to provide easy access to residential or commercial locations. In addition to allowing easy access to the desired location, pipes are buried in order to save space above ground, to create an aesthetically pleasing environment, and to protect the pipes from damage and natural wear that the pipe could possibly be exposed to if they were located on the surface. However, pipes located underground still periodically need maintenance, or even to be replaced.
Before beginning maintenance or replacement on these underground pipes, they must first be located. Many times there are not readily available, or otherwise up to date, construction blueprints outlining the location of the buried pipe. In the case that blueprints are available for use, it is still common practice to employ a locating scheme in order to prevent erroneous digging. Furthermore, digging in locations that are mistakenly offset by less than a foot frequently results in damage to the pipe. If the pipe are metallic, it may be possible to locate the pipes through the use of some sort of metal detector. However, this technique does not apply to locating non-metallic pipes, such as pipes formed of plastic.
Therefore, a need exists to accurately and precisely locate underground pipes once buried, regardless if the pipe makeup is metallic or plastic. Present day means for solving this problem typically involve using tracer wire or magnetic location tape placed on the pipe itself. Tracer wire and magnetic location tape are used in conjunction with an electronic pipe finder. Tracer wire is typically a 12 gauge, coated, copper wire with watertight connecting splices. The tracer wire can be installed on top of the pipe or on the bottom. Tracer wires work reasonably well, but have a short lifetime once buried underground due to the effects of electrolysis. Once the tracer wire is installed, electronic pipe finders, which usually consist of a component to send a signal and a component to pick up a signal, are employed to locate the pipe. The transmitter component induces an electromagnetic field into any metallic objects buried into the ground within its range. As a receiver is carried over and across a pipe location, the induced electromagnetic field is detected by the receiver, thereby providing the user with the location of the buried pipe.
There are also several mechanical designs which have been used to locate underground pipe. U.S. Pat. No. 5,151,657 teaches an apparatus intended to be used with equipment that is inserted into an underground pipe of conduit. The invention includes a head that is attached to a member such as a hose or cable that has a wire attached thereto along its length. In order to function, the invention requires access to a known location of the underground pipe. The hose or cable is fed into a known opening in the pipe and allowed to travel a desired distance. The wire is connected to a signal generator which provides a signal to be detected by a receiver above ground to provide the location of the member and its depth, thereby supplying a method to track the direction, depth, and location of the buried pipe.
Various solutions have been proposed, as an alternative to the above process, to automate the locating process of buried pipes. These inventions most commonly involve the use of either acoustic signals or various other types of readers. For example, U.S. Pat. No. 6,003,376 teaches an acoustic method and apparatus for measuring the horizontal surface location and depth of any type of underground pipe, or conduit. The method applies to nonmetallic or nonconductive pipe, which cannot be detected with electromagnetic locators. A continuous-wave acoustic signal is injected into and transmitted through the fluid in the pipe. The horizontal surface location and depth of the pipe are determined from an analysis of the phase measurements derived from an array of acoustic measurements, which are made at the surface and approximately perpendicular to the direction of the underground pipe. However, this and similar systems are complex and expensive to purchase and maintain.
U.S. Pat. No. 6,252,538 discloses a system for locating and identifying underground pipes which utilizes a ground-probing radar, including an antenna module and a transmit/receive sub-system. Through a complex system of digital signal processing and data extraction, the invention detects differences in dielectric constants with a master controller. The system further includes a positioning sub-system, a display sub-system, a user interface and a data storage mechanism.
From the foregoing discussion, it should be apparent that a need continues to exist for improved locating technology that can quickly and accurately locate any number of underground pipe or pipe components.
A need also exists for such a locating technology that is easy to use and economical to manufacture, and yet is robust and tolerant and capable of functioning for an extended life time.
A need also exists for locating pipes which are in hidden locations other than below ground, for example, behind walls in a building.